1. Field of the Invention
The present invention relates to a force-feedback input device used for, for example, car navigation systems and, in particular, to an improvement in the operational sensation of an input device having a function of automatically attracting a cursor into a position of a menu-selection button displayed on display means in order to facilitate the selection of a desired button.
2. Description of the Related Art
Input devices are known in which display means displays menu-selection buttons and a cursor, and in which input means allows an operator to select a desired menu by moving the cursor to the display position of the desired button among the menu-selection buttons. In addition, some input means have a function that automatically attracts a cursor to the displayed position of the button to facilitate a movement of the cursor to the displayed button position.
FIG. 9 is a block diagram of a known input device having an automatic cursor attraction function. This input device includes input means 101 which is operated by an operator and detects the amount of movement by itself, display means 102 which displays a cursor moved by the input means 101 and input points (buttons), position detecting means 103 which finds the coordinates of the cursor displayed on the display means 102 from the amount of movement of the input means 101, and driving means 104 for providing force-feedback to the input means 101 in accordance with the coordinates of the position of the cursor. The input means 101 includes a rolling ball 105 which moves on a desk while rotating, and rotation-angle detecting means 106 and 107 disposed in accordance with the x-axis and y-axis directions of the display means 102 in order to detect the amount of rotation of the rolling ball 105 in the x-axis direction and in the y-axis direction. The driving means 104 includes a driving unit 108 composed of motors 108a and 108b to drive the rolling ball 105 and a driving signal generation unit 109 for generating a driving signal to drive the driving unit 108 in accordance with a signal from the position detecting means 103 (refer to, for example, Japanese Examined Patent Application Publication No. 07-120247).
As shown in FIG. 10C, the driving signal generation unit 109 pre-stores a relationship among a relative distance between a cursor and an input point, a relative moving direction of the cursor towards the input point, and a driving signal supplied to the driving unit 108. As shown in FIG. 10A, when the cursor is moved towards the input point by the operation of the input means 101 and the cursor enters the range of x1≦x≦x2, the driving signal “+1” shown in FIG. 10C is supplied to the driving unit 108 from the driving signal generation unit 109. Accordingly, a driving force is provided to the rolling ball 105 so that a sensation is provided to the input means 101 as if it is attracted by the input point, as shown in FIG. 10B, and the cursor is attracted to the input point. In contrast, when the cursor is moved away from the input point by the operation of the input means 101 and the cursor enters the range of x3≦x≦x4, the driving signal “−1” shown in FIG. 10C is supplied to the driving unit 108 from the driving signal generation unit 109. Accordingly, a resistive force is provided to the rolling ball 105 so that a sensation is provided to the input means 101 as if it is pulled back by the input point.
Therefore, an input device of the above-described structure facilitates the operation for a cursor to move on the desired input point. For example, this input device facilitates the menu selection displayed on the display means 102.
In the above-described known example, it is designed such that, when the cursor moves into a predetermined area for an input point, the cursor is attracted to the display area of the input point by applying a driving signal to the driving unit 108. In addition, in some of the known input devices, a cursor is attracted to the closest input point even when the cursor is placed at any location outside the display area of the input point. That is, the input devices have an infinite attractive area.
Additionally, in the above-described known example, the cursor is not attracted to the center of the input point. However, some of the known input devices move a cursor into the center of the input point.
Furthermore, in the above-described known example, a mouse is used as the input means 101. However, some of the known input devices employ a joystick instead of a mouse.
As described in Japanese Examined Patent Application Publication No. 07-120247, a plurality of menu selection buttons (input points) is normally disposed on display means in various ways. However, the technology described in the publication discloses no method for controlling an attractive force when a plurality of buttons is displayed on display means, in particular, when the buttons are closely located to each other. That is, the strength of the attractive force is controlled based on only the distance between a cursor and one of the buttons. Therefore, when the technology described in that publication is applied to an actual device, and a cursor is moved from the display position of one button or the vicinity of the button to the display position of another button or the vicinity of the button, impact strength occurs in the input means, and therefore, the operability of the input means becomes degraded or the cursor cannot be smoothly moved in the desired direction, which is a problem.
In other words, when a plurality of buttons is displayed on display means, a cursor is attracted in the direction towards the closest displayed button of the cursor. Accordingly, if the closest button changes to another button and the direction of the attractive force is switched while the cursor is moving, the strength of the attractive force abruptly changes. Therefore, unless the strength of the attractive force exerted on the input means is reduced before and after the change, a large impact strength occurs in the input means.
As shown in FIG. 11, two buttons B1 and B2 are displayed in the x-axis direction of the display means 102. The attractive force of a cursor C is determined based on only a distance between the cursor C and the button. For example, the strength of the attractive force is constant. When the cursor C moves from the left of the button B1 to the right of the button B2 on a line M1 between a center O1 of the button B1 to a center O2 of the button B2, a component force Fx of the attractive force in the x-axis direction and a component force Fy of the attractive force in the y-axis direction, as shown in FIG. 12A, are provided to the input means 101 by two driving means, for example, the motors 108a and 108b, disposed along the x-axis direction and the y-axis direction. If the cursor C moves from the left of the button B1 to the right of the button B2 on a line M2 parallel to the line M1, a component force Fx of the attractive force in the x-axis direction and a component force Fy of the attractive force in the y-axis direction, as shown in FIG. 12B, are provided to the input means 101 by the two driving means.
As can be seen from FIGS. 12A and 12B, when an attractive force exerted on the cursor C is controlled only by a distance between the cursor C and a button regardless of the displayed position of the cursor C with respect to the buttons B1 and B2, the direction of a component force Fx of the attractive force in the x-axis direction is reversed at the time when the cursor C passes across the mid-point between the center O1 of the button B1 and the center O2 of the button B2, that is, when the cursor C passes across a center line Y-Y between the buttons in FIG. 11. Accordingly, the strength of the attractive force abruptly changes and, thus, an unnatural click sensation occurs from button to button and provides an operator with an unpleasant sensation.